1. Field of the Invention
The present invention relates to an exhaust emission control system of an engine, including a hydrocarbon trap for adsorbing hydrocarbon (HC) at a low temperature, and a catalytic converter capable of being activated at a high temperature, in which the trap and converter are incorporated in an exhaust system of an engine so as to remove hydrocarbon and other harmful components contained in an exhaust gas from the engine.
2. Description of the Prior Art
In a prior art exhaust emission control system of this type, as disclosed in Japanese Patent Application Laid-open No.141816/91, an adsorbing trap and a catalytic converter are incorporated in series in sequence from an upstream side in an exhaust pipe connected to an aggregated pipe of an exhaust manifold. Therefore, this prior art exhaust emission control system suffers from a problem that the exhaust gas is cooled by the exhaust manifold, which has a large heat mass, before the exhaust gas from a combustion chamber reaches the catalytic converter. Therefore, because the catalyst must be hot to function properly, it takes a long time for the catalytic converter to be activated after the start of the engine.